Quinone phosphates as lubricant additives

ABSTRACT

Quinone phosphates, including pentoxyphosphoranes, have been found to be effective oxidation and corrosion inhibitors in lubricating oils, especially synthetic ester oils.

United States Patent Metro et a1. 1 1 June 20, 1972 541 QUINONE PHOSPHATES AS 1561 References cited LUBRICANT ADDITIVES UNITED STATES PATENTS [72] v rs; Stephen J. Metro, Scotch Plains; Haro 3,558,747 1 1971 Meltsner ..252/49.8 x Shaub, New Pr vi n h of 2,553,417 5/1951 Ladd et a1. ....252/49.8 X 2,990,420 1/1961 Gleim et al.. ....252/49.8 X [73] Assgnee' Research and Engineer Cmnpany 3,325,567 6/1967 Le Suer ..242/49.s x [22] Filed: Aug. 21, 1970 Primary Examiner-Daniel E. Wyman 1 pp 66,077 Assistant Examiner-W. Cannon Att0meyPear1man and Schlager and Carl G. Seutter 57 ABSTRACT [52] U.S. C1 ..252/49.8, 260/964 Quinone phosphates, including pentoxyphosphoranes, have 5 1 Cl, C10 1/46 been found to be effective oxidation and corrosion inhibitors 58 1 Field 61 Search ..252/49.8 in lubricating Oils, especially Synthetic ester oils- 11 Claims, No Drawings QUINONE PHOSPHATES AS LUBRICANT ADDITIVES FIELD OF THE INVENTION DESCRIPTION OF THE PRIOR ART The problem of deterioration of lubricating oils and formation of harmful deposits under high performance service conditions has been the cause of much concern in providing satisfactory lubrication of internal combustion engines. This problem is especially acute in lubricating engines of the gas turbine type eg. turbojet, turboprop and turbofan engines, where lubricants encounter extremely high temperatures. These severe service conditions, which favor oxidation reactions, may break a lubricant down into harmful acidic products which attack the metal parts of the engine or which may act as further oxidation catalysts. The problem is especiully serious with regard to magnesium corrosion. Magnesium, which is finding ever-increasing use as a constituent of light-weight metal engines, is especially susceptible to attack by the acidic products of a deteriorated lubricant. In recent years it has been the practice to incorporate into lubricating oils additive compositions to inhibit oxidation and corrosion. Many of these prior art compounds, however, have been found to be unacceptable for use in jet type engines. Investigation has shown that these compounds, at high temperatures, may become extremely corrosive to engine parts.

It is an object of this invention to provide a lubricant additive which is effective as a corrosion and oxidation inhibitor. Other objects will be apparent to those skilled in the art.

SUMMARY OF THE INVENTION In accordance with certain of its aspects, this invention is directed to lubricating compositions comprising a major amount of a lubricating oil and a minor corrosion and oxidation inhibiting amount of a quinone phosphate. The quinone phosphates may be characterized by the formula benzene, naphthalene, pyrene, anthracene, and phenanthrene; and n is an integer 4.

DESCRIPTION OF THE INVENTION The quinone phosphate compounds which may be used in practice of this invention may be prepared by the reaction of a quinone with a phosphite. The quinone compounds may be:

wherein R may be a hydrocarbon, Ar is a quinoid ring derived from a hydrocarbon nucleus selected from the group consisting of benzene, naphthalene, pyrene, anthracene, and phcnnnthrcnc nuclei, and n is an integer O 4.

Preferably Ar is an unthracenc nucleus and the quinone is an anthraquinonc:

Typical quinones may include o-quinone. i.e. o-benzoquinone; p-quinone; anthraquinone; alpha or beta naphthaquinone; pyrenediquinone (eg. 4,5,9,lO-pyrenediquinone); 1,4- dihydroxy, anthraquinone (i.e. quinizarin); quinizarin dilaurate; etc., including inertly-substituted quinones, eg. 2,3- dimethyll ,4-naphthoquinone; Z-methyll ,4-naphthoq uinone; 2,3-dimethyl-anthraquinone; 2-methoxy-l ,4-naphthoquinone; 2-ethyll ,4 naphthoquinone; 2-propyl-anthraquinone; etc. Inertly-substituted quinones may be employed including those bearing eg. hydrocarbon, alkoxy, etc. substituents.

These quinones may be reacted with phosphites P( OR In the phosphite (ROMP, R may be a hydrocarbon moiety, typically alkyl. When R is alkyl, it may be methyl, ethyl, propyl, ipropyl, n-butyl, i-butyl, t-butyl, hexyl, octyl, etc. When R is cycloalkyl, it may be cyclohexyl, etc. The R group may be inertly substituted, ie it may bear a substituent which does not react with the other components of the process or interfere with the reaction. Typical inert substituents may include ether, alkyl, etc. Typical inertly-substituted R radicals may inelude 2-ethyl-hexyl, ethoxyethyl, methylcyclohexyl, etc. All the R groups in a particular compound need not be the same; preferably however, they may be the same. More preferably, R may be alkyl and more preferably, lower alkyl having one to l0 carbon atoms.

Preparation of the additives used in practice of this invention may typically be effected by the reaction of a phosphite (I) P(OR) with a quinone typically having the following formula:

Reaction may be carried out typically as follows:

(IV) (I (OCOR)n Preferably reaction may be carried out (q.v. Ramirez et al. J. Org. Chem. 33 January 1968. page 20-24) by maintaining the reactants, typically in inert solvent such as benzene, at reflux temperature under nitrogen. After typically 20-24 hours at reflux, the solvent may be evaporated and the typically yellow oil water washed and crystallized. Commonly recrystallization may be effected from a mixture of benzene and hexane.

When n is other than 0, the quinone compounds may be prepared by the process of US. Pat. No. 3,470,099, and the OCOR group will preferably be on a ring other than that bearing the quinone structure. a

Typical of specific quinone phosphates which may be employed in practice of this invention may be the following:

(XIII) The preferred compound may be compound (V111) prepared by the reaction of anthraquinone and trimethyl phosphite.

A preferred class of quinone phosphates which may be used in practice of this invention may be those prepared from acylated quinones with trialkyl phosphates. Typical of these may be acylated quinizarin:

(XXXII) in these compounds, R may be selected from the same group as that from which R supra may be selected; but preferably R may be a long-chain alkyl, preferably containing 8-18 carbon atoms.

These compounds may be prepared by the reaction of a phosphite, such as trimethyl phosphite, with an acylated quinone, such as quinizarin dilaurate. Reaction may be effected by reacting the acylated quinone with an excess of alkyl phosphite at reflux in an inert atmosphere. After reflux for up to 24 hours, the excess phosphite may be stripped off under vacuum; and the residue is dissolved in inert solvent, such as ethyl ether, washed with dilute base, dried, and stripped of solvent.

Although the products appear to be of high purity, based upon elemental and spectroscopic analysis, by-products formed (which need not be removed) may include:

i (go (CHDwCHa (XXXIII) illustrative compounds in this class ma include: a. 10-methoxy-9-hydroxyanthracene dimethyl phosphate 1 ,4-dilaurate; b. 10-ethoxy-9-hydroxyanthracene diethyl phosphate 1.4-

distearate; c. 2-methyl-10-methoxy-9-hydroxyanthracene dimethyl phosphate 1,4-dilaurate;

d. 4-methoxy-1-hydroxy naphthalene dimethyl phosphate 5,8-dilaurate; e. 2-methyl-4-methoxy-1-hydroxy naphthalene dimethyl phosphate 5 ,8-dilaurate; f. 6-methyl-4-methoxy-1-hydroxy naphthalene dimethyl phosphate 5,8-dilaurate; The preferred compound in this class may be the reaction product of quinizarin dilaurate and trimethyl phosphite:

i.e. lO-methoxy-9-hydroxy anthracene dimethyl phosphate 1 ,4-dilaurate.

In practice of the novel process of this invention, the quinone phosphates may be added to the lubricating composition in a minor corrosion and oxidation inhibiting amount. Typically, such an amountv may be 0.01 5 percent by weight, preferably 0.1-4 weight percent, say 0.1-1 weight percent, typically 0.5 weight percent.

The lubricating oil which may be improved by the technique of this invention may preferably include synthetic ester oils such as high molecular weight, high-boiling liquid aliphatic dicarboxylic acid esters or dior trior tetra-esters of hindered polyols. The viscosity of these oils (when treated in accordance with practice of this invention) may typically be 3.0-8.0 cs at 210 F.

When the base fluid is an ester it may be prepared from various combinations of aliphatic monocarboxylic acids and dicarboxylic acids having from about five to 36 carbon atoms, and monohydric and polyhydric aliphatic alcohols having from about four to about 20 carbon atoms. Specific examples of these esters that may be used are: di-iso-octyl adipate. didecyl azelate, di-isodecyl azelate, di-isodecyl adipate, ditridecyl adipate, di-iso-octyl sebacate, di-isodecyl sebacate. di-2-ethylhexy1 sebacate, di-iso-octyl dodecanedioate. di-2- ethylhexyl azelate, and di-2-ethy1hexyl adipate. Other esters may also be used as synthetic lubricants that are made from hindered polyols and monoand polycarboxylic acids of about five to 13 carbon atoms.

The base oil is a hindered polyester having at least two ester linkages per molecule; it therefore includes diesters such as neopentyl glycol dipelargonate and di(2,2,4-trimethylpentyl) sebacate. The term neutra1" is used to mean a fully esterified product.

It is to be understood that in the esterification reaction, there may be used more than one of any of the reactants mentioned e.g. a mixture of monocarboxylic acids, and in any case, the neutral ester product of the esterification reaction will sometimes consist of a mixture of diflerent ester molecules, so the expression polyester" is to be construed in this light.

Examples of suitable acids and alcohols that may be used in the preparation of the polyester are caprylic acid, capric acid, caproic acid. enanthic acid, pelargonic acid, valeric acid, pivalic acid, propionic acid, butyric acid, 2-ethylhexanoic acid, adipic acid. sebacic acid, azelaic acid, 2,2,4-trimethylpentanol, neopentyl alcohol, neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol and dipentaerythritol.

The most suitable polyesters are the esters of trimethylolpropane, trimethylolbutane, trimethylolethan, pentaerythritol and/or dipentaerythritol with one or more monocarboxylic acids having three to carbon atoms, particularly one or more of those mentioned in the previous paragraph, and more complex esters. for example those prepared from timethylolpropane. sebacic. adipic, and/or azelaic acid, and one or more monocarboxylic acids having three to 10 carbon atoms, particularly one or more of those mentioned in the previous paragraph.

Illustrative ester-type lubricating oils may include:

TABLE di-Z-ethylhexyl sebacate di-2-ethylhexyl azelate di-Z-ethylhexyl adipate di-n-amyl sebacate di-Z-ethylhexyl-n-dodecyl succinate di-Z-ethoxyethyl sebacate trimethylolpropane tripelargonate trimethylolpropane tricaproate trimethylolpropane tricaprylate trimethylolpropane tri-neoheptanoate trimethylolpropane tri-n eodecanoate trimethylolpropane mono-neoheptonate dipelargonate di(C,,-C,,,-oxoalcohol) adipate tetra (C monocarboxylic acid) esters of pentaerythritol These oils may be blended with other oils, such as castor oil; lard oil; polymerized olefins; copolymers of alkyleneglycols or aliphatic alcohols with organic acids, etc.

The additives of the present invention may be used alone or preferably in combination with other additives in a lubricating composition. These other additives, typically present in amount of 0.001 10 weight percent each may include:

a. oxidation inhibitors such as aromatic amines e.g. phenothiazine;

b. metal corrosion inhibitors such as benzotriazole;

c. load-carrying agents, such as tricresyl phosphate;

d. anti-foamants such as a silicone;

e. dispersants such as the polymethacrylates.

The novel compositions of this invention may include concentrates of quinone phosphates (which may be added to lubricating compositions) in inert diluents including lubricating compositions, solvents, eg. esters, in amount of IO 90 percent; and these concentrates may include other additives.

Addition of quinone phosphate to lubricating oils in accordance with the technique of this invention permits attainment of outstanding results when the composition is subjected to The Oxidation Corrosion Stability Test which is carried out by suspending metal pieces in oil. Dry air is bubbled at 5 liters per hr. through 100 g. of oil at 425 F. for 72 hours. These tests simulate to a degree the operating conditions of jet engines. At the end of the test, the following may be determined:

a. the corrosion of each metal tested in mg/cm b. the percent increase in centistoke viscosity; and

c. the increase in total acid number (TAN).

This OCS Test is similar to Military Specification MlL-L7 S08-G except that the OCS test is run at 425 F. instead of 347 F.

In typical Oxidation Corrosion Stability Tests it may be found that use of the novel systems of this invention permits attainment of substantially decreased weight loss for magnesium under severe oxidative conditions.

It may also be found that the increase in total acid number (TAN) is substantially smaller than that attained without use of the additives of this invention. Commonly it is found that the A kinematic viscosity is significantly reduced by the use of the instant invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Examples l-IV In these examples, which represent a preferred embodiment of the invention, the quinone phosphate (Compound A was prepared from a commercially-available hydrocarbon mixture, having an average molecular weight of about 300, and containing substantial proportions of alkylated aromatics. This composition may be oxidized to form the corresponding quinone by the method of US. Pat. No. 2,373,003 to Arnold. In this oxidation, I00 g. of alkylated aromatic may be mixed with l,000 ml. of glacial acetic acid, 500 ml. of 30 percent hydrogen peroxide added dropwise over a 30-minute period, and the reaction mixture refluxed for 22 hours. The acetic acid and water was then stripped under vacuum.

The crude reaction product was dissolved in I000 ml. of ethylether, the mixture filtered and washed with 3 X 250 ml. of 5 percent sodium bicarbonate solution, followed by 2 X 250 ml. water.

The resulting ether solution was dried and the ether stripped. 70.3 g. of product was obtained. The lower phase of the product mixture, 48.8 g. was separated. Infrared analysis showed presence of quinone structure.

48.8 g. of this product was mixed with g. (1 mole) of trimethyl phosphite; and the mixture was refluxed for 24 hours under a blanket of nitrogen. The excess of trimethyl phosphite was stripped off under vacuum. The crude reaction product was dissolved in 1,000 ml. anhydrous ethyl ether. The ether solution was twice washed each time with 250 ml. of aqueous sodium bicarbonate and then twice with 250 ml. water. The ether solution was then dried, and the ether removed by evaporation under nitrogen. The product was then vacuum desicated for 12 hours to remove remaining traces of water and ether. The product, Compound A, was obtained in yield of 40 grams.

The Base Lubricating Oil which was employed contained the following:

Parts Component 70 Trimethylol propane ester of C average monocarboxylic acids. 30 Dipentaerythritol ester of C average monocarboxylic acids. 1.3 p,p'-Dioctyl diphenyl amine. l.l Phenyl a -naphthylamine. 0. l Benzotriazole. 0.02 Sebacic acid. 0.00! Silicone.

With the base oil, the following compositions were formulated:

TABLE Metal weight loss, mgJcrn.

Mg Fe A1 Ag Ti Norm-425 F. 72 hour 008 test.

From this table, it will bea pparent that the weight loss of magnesium is desirably decreased. Although the base oil alone permitted a loss of 11.74 mg/cm", use of the technique of this invention in Example III permitted a loss of only 1.50 mglcm i.e. a drop to only 12.7 percent (a tenfold reduction) of that recorded with the base oil alone. Simultaneously the weight losses with copper, iron, aluminum, silver, and titanium all were either bettered (i.e. decreased) or desirably showed little or no change.

Examples V-Xll In Examples V and VI, which represent a more preferred embodiment of the invention, the quinone phosphate (Compound B) was quinizarin dilaurate phosphate product prepared by the reaction of (a) one mole of quinizarin dilaurate (i.e. l,4-dilauroyl-9,lO-anthraquinone) and (b) one mole of trimethyl phosphite.

Specifically 63.4 g. (0.1 mole) of quinizarin dilaurate was dissolved in 125 g. (1 mole) of trimethyl phosphite in a reaction vessel. The mixture was refluxed for 24 hours under a blanket of nitrogen. The excess of tn'methyl phosphite was then stripped off under vacuum. The crude reaction product was dissolved in 1,000 ml. anhydrous ethyl ether. The ether 561366.135; twice washed, each time with 250 ml. of aqueous sodium bicarbonate and then twice with 250 ml. of water. The ether solution was then dried, and the ether removed by evaporation under nitrogen. The product was then vacuum dessicated for 12 hours to remove remaining traces of water and ether.

In Examples VII and VIII, the quinone phosphate (Compound C) was the quinizarin dioctanoate phosphate product prepared by the reaction of (a) one mole of quinizarin dioctanoate and (b) one mole of trimethyl phosphite. This product was prepared by the same process as that of Examples V and VI except that the charge material was quinizarin dioctanoate.

The following compositions were formulated:

V. Base oil, 100 parts, plus 0.1 parts of Compound B.

VI. Base oil, 100 parts, plus 0.05 parts of Compound B.

VII. Base oil, 100 parts, plus 0.1 parts of Compound C.

VIII. Base oil, 100 parts, plus 0.5 parts of Compound C.

IX. Base oil, 100 parts, plus 0.05 parts quinizarin dilaurate.

X. Base oil, 100 parts, plus 0.1 parts quinizarin dilaurate.

XI. Base oil, 100 parts, plus 0.1 parts quinizarin disctanoate.

XII. Base oil, 100 parts, plus 0.5 parts quinizarin dioctarloate.

When these compositions were subjected to the OCS test, supra, the following were noted. Examples I and II are repeated for convenience. It will be noted that Example 11 is reported in quadruplicate, and Examples V and VI in duplicate.

is well within the dilaurate and quinizarin dioctanoate, not within the scope of this invention, yielded results which were unsatisfactory particularly with respect to:

a. copper and magnesium corrosion; and

b. viscosity increase.

It will also be apparent that preferred Example Vlll permits attainment of a formulation which may be characterized by:

a. satisfactory initial and final viscosity;

b. satisfactory initial and final acid number;

c. satisfactory oxidation-corrosion properties with respect to copper, iron, aluminum, silver, and titanium; and

d. outstanding reduction (almost elimination) of oxidationcorrosion of magnesium.

In other comparative OCS tests (under standard specification MIL-b23699) carried out at 400 F., it was observed that the loss of copper from a copper coupon averaged 2.49 mg/cmin the presence of base oil alone, 0.035 mg/cm in the presence of base oil containing quinizarin dilaurate-methyl phosphate, and 0.36 mg/cm in the presence of base oil containing the same amount of quinizarin dilaurate.

In the case of a magnesium coupon, the corresponding numbers were0.19,0.015,and 0.17.

The percent change in viscosity was found similarly to be 36.1, 19.7, and 26.2.

From these data, it may be concluded that the base oilaitaining quinizarin dilaurate-methyl phosphate of this invention reduces copper corrosion by a factor of 10 (as compared to quinizarin dilaurate alone) and by a factor of about 70 (as compared to the base oil alone).

Similarly the base oil containing quinizarin dilaurate-methyl phosphate of this invention reduces magnesium corrosion by a factor of 10 (as compared to quinizarin dilaurate alone) and by a factor of 10 (as compared to the base oil alone).

In the case of viscosity, it was noted that the Base Oil and the Base Oil containing quinizarin dilaurate were above the set specification of 25 (%A viscosity at 100 F. measured after the 400 F. test) of MIL-b23699. The percent viscosity change of the Base Oil containing quinizarin dilaurate-methyl phosphate was 19.7 percent which is well below the maximum specification of 25 percent set by specification MIL-L-23699.

Thus, it will be noted that practice of this invention yields a product which is eminently satisfactory in the respect to the 425 F. OXIDATION-CORROSION STABILITY TEST (OCS) 72 HOURS New oil Metal weight loss, .mgJcm. Used oil t Percen Oil KV/IOO Tan Cu Mg Fe Al Ag Ti KV/lOO Tan AKWIOO Atan -11. 74 +0. 01 +0. 01 0. 01 279. 2 4. 33 959. 98 4. 03 9. 78 +0.01 +0. 02 0. 01 39. 72 4.47 54. 25 4. O8 -7. 92 +0. 03 0. 00 0. 01 39. 63 6. 09 53. 25 5. 70 12. 20 +0. 03 0. 00 +0. 01 40. 44 4. 75 10. 23 +0. 03 +0. 03 0. 00 40. 17 4. 33 5. 05 +0. 02 0. 00 0. 01 37. 68 4. 26 42. 51 3. 37 -5. 4.5 +0. 03 0. 00 0. 01 38. 85 5. 43 46. 4. 76 0. 87 +0. 02 +0. 01 -0. 03 38. 40 7. 18 -0. 40 +0.02 +0.01 0. 04 88. 22 7.36 1. 47 +0.03 0.00 -0. 09 37. 23 6. 25 40.23 5.91 0. 09 +0. 03 +0. 01 0. 01 36. 66 6. 04 36. 18 5. 55 -11. 06 0. 01 +0. 01 0. 01 123. 4 5. 32 368. 67 4. 96 8. 01 0. 01 +0. 01 0. 01 116. 2 4. 76 342. 33 4. 39 10.02 +0.01 +0.01 0. 01 123. 3 5.12 367. 58 4. 81 12. 53 0. 01 +0.01 0. 01 113. 3 6. 21 326. 74 5. 83

From the above table, it will be nofedtliai tleweight loss parameters of the 400 F. oxidation test while the Base oil for magnesium in Example v is about halfthat of control Exalone 0! containing Cg. quinizarin dilaurate fails on 1656 amples I-ll. More unexpectedly, the weight loss for magnesi- Countsum in Examples VI-VIII is substantially lower; and the loss in e lubflcanns 011$ whlch y be Improved y the Example vm is outstandingly [om technlque of this invention may be synthetic ester oils, The weight loss for other metals in Examples V-VII is also Preferably hlgh molecular Weight, high-boiling ester oils characterized as low and well within the specified limits. formed yp f y from n aliphatic, carboxylic acid and Unexpectedly it is noted that the change in kinematic Preferably a hlndered polyol. Such oils may commonly have a viscosity (when treated by the process of this invention) of 3.0 8.0 cs at 210 F.

The lubricating oil may be a synthetic ester oil formed by the reaction of a C -C acid and a C C- alcohol. According to one aspect of this invention, the oil may preferably be formed from (a) a C -C aliphatic acid R(COOH), wherein R is an aliphatic hydrocarbon (including inertly-substituted hydrocarbon) residue and n is typically 1-3 and (b) a C -C aliphatic alcohol R'(OH),,, wherein R is an aliphatic hydrocarbon (including inertly-substituted hydrocarbon) residue and m is an integer preferably 1-6, most preferably 1-3.

The base oil may, in one embodiment, be a liquid ester product of an aliphatic monocarboxylic acid and a polyol. Preferably the aliphatic monocarboxylic acid may have the formula R(COOH) wherein R is an aliphatic hydrocarbon moiety.

The preferred of these acids may be C -C preferably C -,C acids. Typical of such acids may be:

caproic acid C caprylic acid C capric acid C enanthic acid C pelargonic acid C valeric acid C pivalic acid C propionic acid C; butyric acid C, Z-ethylhexanoic acid C The polyols which may be reacted with the noted aliphatic monocarboxylic acids, to form esters, may include R'(OH),, wherein R is an aliphatic moiety and m is an integer preferably 2-6, more preferably 2-4. The preferred polyols may be the C -C say C -C polyols. Typical of such polyols may be:

neopentyl glycol trimethylol ethane trimethylol propane trimethylol butane pentaerythritol dipentaerythritol Typical esters of aliphatic monocarboxylic acids and polyols may be )m including the following illustrative examples:

TABLE pentaerythritol tetra-valerate pentaerythritol tetra-caproate pentaerythritol tetra-2-ethylhexanoate pentaerythritol tetra-pelargonate pentaerythritol tetra-butyrate dipentaerythritol hexa-valerate dipentaerythritol hexa-pelargonate dipentaerythritol hexa-caprate trimethylol propane tri-caproate trimethylol propane tri-butyrate trimethylol propene tri-valerate trimethylol propane tri-pelargonate In another embodiment, the base oil may be a liquid synthetic ester product of an aliphatic polycarboxylic acid and an aliphatic monohydroxy alcohol.

Preferably the aliphatic polycarboxylic acid may havethe formula R(COOH),, wherein n is greater than 1 and preferably 2-3. Typical polycarboxylic acids may include:

adipic acid azelaic acid se bacic acid dodecanoic acid Illustrative of the esters so formed may be: di-2-ethylhexyl sebacate; di-2-ethylhexyl adipate; di-2-ethylhexyl azelate; di- C -oxo alcohol sebacate; di-2-ethylbutyl pivalate; and di- 3,5,5-trimethyladipate.

Although this invention has been illustrated by reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made which clearly fall within the scope of this invention.

What is claimed is:

l. A lubricating composition comprising:

a. a major amount of lubricating oil; and

b. a minor corrosion and oxidation inhibiting amount of a phosphate of a hydroquinone having the formula:

wherein R and R are each a hydrocarbon; Ar is selected from the group consisting of benzene. naphthalene. pyrene, anthracene, and phenanthrene. and n is an integer 0-4.

2. A lubricating oil composition as claimed in claim 1 wherein the lubricating oil is a synthetic ester lubricating oil.

3. A lubricating composition as claimed in claim 1 wherein n is 0.

4. A lubricating composition as claimed in claim 1 wherein n is 2.

5. A lubricating composition as claimed in claim 1 wherein R is a C to C alkyl group and R is a C to C long-chain alkyl group.

6. A lubricating composition as claimed in claim 1 wherein said compound is i RO- OR 8. A lubricating composition as claimed in claim 1 wherein said compound is:

if 1"OR O OCOR wherein R and R are each a hydrocarbon.

9. A lubricating composition as claimed in claim 1 wherein said compound is:

11. A lubricating composition as claimed in claim 1 wherein H 0 CH said compound is CHaO- [0. A lubricating composition as claimed in claim 1 wherein CH n is 2 and R is C, to C,,,. 

2. A lubricating oil composition as claimed in claim 1 wherein the lubricating oil is a synthetic ester lubricating oil.
 3. A lubricating composition as claimed in claim 1 wherein n is
 0. 4. A lubricating composition as claimed in claim 1 wherein n is
 2. 5. A lubricating composition as claimed in claim 1 wherein R is a C1 to C10 alkyl group and R'' is a C8 to C18 long-chain alkyl group.
 6. A lubricating composition as claimed in claim 1 wherein said compound is
 7. A lubricating composition as claimed in claim 1 wherein said compound is:
 8. A lubricating composition as claimed in claim 1 wherein said compound is:
 9. A lubricating composition as claimed in claim 1 wherein said compound is:
 10. A lubricating composition as claimed in claim 1 wherein n is 2 and R'' is C8 to C18.
 11. A lubricating composition as claimed in claim 1 wherein said compound is 